Biology MCQs for Class 12 with Answers Chapter 13 Organisms and Populations

Free PDF Download of CBSE Biology Multiple Choice Questions for Class 12 with Answers Chapter 13 Organisms and Populations. Biology MCQs for Class 12 Chapter Wise with Answers PDF Download was Prepared Based on Latest Exam Pattern. Students can solve NCERT Class 12 Biology Organisms and Populations MCQs Pdf with Answers to know their preparation level.

Organisms and Populations Class 12 Biology MCQs Pdf

1. Animals from colder climates generally have shorter limbs. This is called
(a) Allen’s rule
(b) Johnson’s rule
(c) Arber’s rule
(d) Niche rule

Answer

Answer: a


2. Niche is defined as
(a) a component of an ecosystem
(b) an ecologically adapted zone of a species
(c) the physical position and functional role of a species within the community
(d) all plants and animals living at the bottom of a water body.

Answer

Answer: c


3. It natality is balanced by mortality in a population at a given time, there will be a/an
(a) decrease in the population size
(b) increase in the population size
(c) zero population growth
(d) population explosion

Answer

Answer: c


4. Mycorrhiza is an example of
(a) ectoparasitism
(b) mutualism
(c) endoparasitism
(d) predation

Answer

Answer: b


5. The interspecific interaction in which one partner is benefitted and the other is unaffected (neutral), is called
(a) amensalism
(b) mutualism
(c) competition
(d) commensalism

Answer

Answer: d


6. Individuals of one kind, i.e., one species occupying a particular geographic area, at a given time form a/an
(a) community
(b) biome
(c) population
(d) deme

Answer

Answer: c


7. The formula of exponential population growth curve, is
(a) dN/dt = rN
(b) dt/dN rN
(c) dN/rN = dt
(d) rN/dN = dt

Answer

Answer: a


8. Niche overlap indicates
(a) mutualism between two species
(b) active cooperation between two species
(c) sharing of one or more resources between the two species
(d) two different parasites on the same host.

Answer

Answer: c


9. Amensalism is an association between two species where [NCERT Exemplar]
(a) one species is harmed and other is benefitted
(b) one species is harmed and other is unaffected
(c) one species is benefitted and other is unaffected
(d) both the species are harmed.

Answer

Answer: b


10. A population has more young individuals compared to the older individuals. What would be the status of the population after some years? ]NCERT Exemplar]
(a) It will decline
(b) It will stabilise
(c) It will increase
(d) It will first decline and then stabilise

Answer

Answer: c


11. Which of the following would necessarily decrease the density of a population in a given habitat? [NCERT Exemplar]
(a) Natality > mortality
(b) Immigration > emigration
(c) Mortality and emigration
(d) Natality and immigration

Answer

Answer: c


12. What parameters are used for tiger census in our country’s national parks and sanctuaries? [NCERT Exemplar]
(a) Pug marks only
(b) Pug marks and faecal pellets
(c) Faecal pellets only
(d) Actual head counts

Answer

Answer: b


13. The organisms which can tolerate and thrive in a wide range of temperature, are called _______ .

Answer/Explanation

Answer:
Explaination: Eury thermal


14. The salinity (measured in parts per thousand) in the sea is ______ .

Answer/Explanation

Answer:
Explaination: 30-35


15. _______ is any attribute of an organism (morphological, physiological and behavioural) that enables it to live and reproduce in the given area. 24 Match the terms in Column I with their

Answer/Explanation

Answer:
Explaination: Adaptation


16. _______ refers to the number of births during a given period of time that are added to the initial density.

Answer/Explanation

Answer:
Explaination: Natality


17. In a logistic growth curve, the final phase is an _______ .

Answer/Explanation

Answer:
Explaination: Asymptote


18. _______ fish breed only once in their life time.

Answer/Explanation

Answer:
Explaination: Pacific salmon


19. An orchid growing as an epiphyte on a mango tree, is an example of _______ .

Answer/Explanation

Answer:
Explaination: Commensalism


20. _______ is an important process as it facilitates energy transfer through various organisms.

Answer/Explanation

Answer:
Explaination: Predation


21. _______ showed that five closely related species of warblers living on the same were able to avoid competitions and co-exist.

Answer/Explanation

Answer:
Explaination: MacArthur


22. Zooplanktons enter, a state of suspended development under unfavourable conditions.

Answer/Explanation

Answer:
Explaination: Diapause


23. Match the terms in Column 1 with those in Column II.

Column I Column II
A. Amensalism 1. The interspecific interaction, where both are equally benefitted.
B. Parasitism 2. The interspecific interaction, where one is benefitted and one is neutral.
C. Mutualism 3. The interspecific interaction, where one is harmed and the other is neutral.
D. Commen­salism 4. The interspecific interaction, where one is benefitted and one is harmed.
E. Competition
Answer/Explanation

Answer:
Explaination: A – 3, B – 4, C – 1, D – 2


24 Match the terms in Column I with their descriptions in Column II.

Column I Column II
A. Home­ostasis 1. Animal which can tolerate a wide range of temperature.
B. Confor­mers 2. The number of births in a given population at a given time.
C. Natality 3. Per capita births in a given population.
D. Eury- thermal 4. A Maintenance of a relatively constant internal environment.
5. Animals which change their body temperature according to the ambient temperature.
Answer/Explanation

Answer:
Explaination: A – 4, B – 5, C – 2, D – 1


25. Zooplanktons enter a state of suspended development, called diapause, under unfavourable conditions. [True/False]

Answer/Explanation

Answer:
Explaination: True.


26. The success of mammals is due to their ability to change their body temperature according to their surroundings. [True/False]

Answer/Explanation

Answer:
Explaination: True.


27. Small animals like shrews and humming birds are rarely found in polar regions. [True/False]

Answer/Explanation

Answer:
Explaination: True.


28. Organisms living in water bodies (lake, sea, river) do not face any water related problems. [True/False]

Answer/Explanation

Answer:
Explaination: False.


29. dSfdt=rN is the equation describing logistic growth. [True/False]

Answer/Explanation

Answer:
Explaination: False.


Directions (Q30 to Q32): Mark the odd one in each of the following groups.
30. Aestivation, Migration, Hibernation, Diapause.

Answer/Explanation

Answer:
Explaination: Migration.


31. Parasitism, Predation, Commensalism, Amensalism.

Answer/Explanation

Answer:
Explaination: Amensalism.


32. Ticks, Lice, Copepods, Tapeworm.

Answer/Explanation

Answer:
Explaination: Tapeworm.


33. Who is considered as the ‘Father of Ecology ’ in India?

Answer/Explanation

Answer:
Explaination: Ramdeo Misra.


34. What is ecology at the organismic level?

Answer/Explanation

Answer:
Explaination: Ecology at the organismic level is essentially physiological ecology, which tries to understand how different organisms are adapted to their environments in terms of not only survival but also reproduction.


35. What causes the annual variation in the intensity and duration of temperature?

Answer/Explanation

Answer:
Explaination:
– Rotation of earth around the Sim.
– Tilt of the earth on its axis.


36. Name the two factors that cause the formation of major biomes.

Answer/Explanation

Answer:
Explaination:
– Variation in the intensity and duration of temperature.
– Variation in precipitation.


37. What does the ecological niche of an organism represent?

Answer/Explanation

Answer:
Explaination: Ecological niche of an organism represents the range of conditions it can tolerate, the resources it utilises and its functional role in the ecosystem.


38. Why are mango trees unable to grow in temperate climate? [AI 2016C]

Answer/Explanation

Answer:
Explaination:
– The levels of thermal tolerance of species determine their geographical distribution, because temperature affects the physiological functions by affecting the kinetics of enzymes.
– Stenothermal organisms (like mango) can tolerate and survive only in a narrow range of temperature, say tropics.


39. Mention the effect of global warming on the geographical distribution of stenothermals like amphibians. [Foreign 2012]

Answer/Explanation

Answer:
Explaination: Stenothermal animals have tolerance to a narrow range of temperatures and hence their geographical distribution would be much affected.


40. Between amphibians and birds, which will be able to cope with global warming? Give reason. [HOTS]

Answer/Explanation

Answer:
Explaination: Birds will be able to cope with global warming; they are eurythermals and can tolerate a wide range of temperatures.


41. How do herbs and shrubs survive under the shadow of big canopied trees in forests?

Answer/Explanation

Answer:
Explaination: The herbs and shrubs growing in the forests are adapted to photosynthesise optimally under very low light conditions.


42. Name a ‘photoperiod’-dependent process, one each in plants and in animals. [Foreign 2013]

Answer/Explanation

Answer:
Explaination:
– Flowering in plants.
– Timing of foraging or migration in plants.


43. Mention any two activities of animals which get cues from diurnal and seasonal variations in light intensity. [Delhi 2011C]

Answer/Explanation

Answer:
Explaination:
(i) Timing their foraging.
(ii) Migratory activities.
(iii) Reproduction. (any two)


44. Why are green algae not likely to be found in the deepest strata of the ocean? [AI 2013] [HOTS]
Or
Why are green plants not found beyond a certain depth in the ocean? [Delhi 2011] [HOTS]
Or
Why are green algae not found at lower depths of a sea? [Delhi 2011C]

Answer/Explanation

Answer:
Explaination: Green algae or plants are not found beyond a certain depth, as light (not all colour components of visible spectrum) is not available.


45. What is the advantage of homeostasis to organisms that exhibit it?

Answer/Explanation

Answer:
Explaination: Homeostasis enhances the overall fitness of organisms because all biochemical reactions and physiological functions proceed with maximal efficiency.


46. Which feature of mammals, is the success rate of them, attributed to?

Answer/Explanation

Answer:
Explaination: Their ability to maintain a constant body temperature irrespective of the environmental temperature.


47. Why have many animals not evolved thermo¬regulation? [HOTS]

Answer/Explanation

Answer:
Explaination: Thermoregulation is an energy-expensive phenomenon; considering the cost and benefit, many animals have not evolved thermoregulation.


48. What are partial regulaters?

Answer/Explanation

Answer:
Explaination: Partial regulaters are those species which have the ability to regulate, but only over a limited range of environmental conditions, beyond which they simply conform.


49. What are osmoconformers?

Answer/Explanation

Answer:
Explaination: Osmoconformers are those organisms which regulate the osmolarity of their body fluids according to their surrounding medium.


50. What is migration?

Answer/Explanation

Answer:
Explaination: Migration refers to the movement of animals from the stressful habitat to a more hospitable area and return to the original place once the stressful period is over.


51. Name the National Park in India where migratory birds arrive in winter from Siberia.

Answer/Explanation

Answer:
Explaination: Keolado National Park, Bharatpur.


52. Mention how bears escape from stressful time in winter. [Delhi 2013C]

Answer/Explanation

Answer:
Explaination: Bears go into hibernation in winter.


53. How do snails escape from the stressful time in summer? [AI2013C]
Or
How do animals like fish and snails avoid summer-related unfavourable conditions? [Delhi 2010]

Answer/Explanation

Answer:
Explaination: Snails and fish go into aestivation in summer.


54. When and why do animals like frog/bear hibernate?

Answer/Explanation

Answer:
Explaination: If the unfavourable (stressful) conditions are for a short duration and if the animals are not able to migrate, they hibernate during extreme winter to avoid the stress by escaping in time.


55. When and why do animals like snails go into aestivation?

Answer/Explanation

Answer:
Explaination: When the snails are not able to migrate from the stressful conditions in the habitat, they undergo aestivation during hot summers to avoid stress by escaping in time.


56. Give an example of an organism that enters ‘diapause’ and why? [Delhi 2014]

Answer/Explanation

Answer:
Explaination:
– Zooplankton.
– It is to tide over the temporary unfavourable conditions in the habitat.


57. How do seed-bearing plants tide over dry and hot weather conditions? [AI 2013C]

Answer/Explanation

Answer:
Explaination: In seed-bearing plants, the seeds and other vegetative reproductive structures serve to tide over the unfavourable conditions; they germinate to form new plants under favourable conditions.


58. Define adaptation.

Answer/Explanation

Answer:
Explaination: Adaptation is defined as any morphological, physiological or behavioural attribute of an organism that enables it to survive and reproduce in its habitat.


59. How do spines help the cactus plants survive in the desert?

Answer/Explanation

Answer:
Explaination:
(i) Leaves are reduced to spines to check transpiration.
(ii) Spines keep away the browsing animals.


60. What is meant by Allen’s Rule?

Answer/Explanation

Answer:
Explaination: Allen’s rule refers to the reduction of heat loss in animals by having shorter ears and limbs.


61. Why is population ecology considered an important area of ecology?

Answer/Explanation

Answer:
Explaination: Population ecology is an important area of ecology, because it links ecology with population genetics and evolution; natural selection operates at the level of population.


62. If 8 individuals in a laboratory population of 80 fruit flies died in a week, then what would be the death rate of the population for the said period? [Delhi 2010]

Answer/Explanation

Answer:
Explaination: The death rate of fruit flies is 8/80, i.e. 100 per thousand or 10 per cent or 0.1 per individual.


63. In a pond, there were 20 Hydrilla plants. Through reproduction, 10 new Hydrilla plants were added in a year. Calculate the birth rate of the population. [Delhi 2010]

Answer/Explanation

Answer:
Explaination: The birth rate of Hydrilla is 10/20, i.e. 500 per thousand or 50 per cent or 0.5 per individual.


64. Define population density.

Answer/Explanation

Answer:
Explaination: Population density refers to the total number of individuals of a species present per unit area or volume at a given time.


65. Provide an instance where the population size of a species can be estimated indirectly, without actually counting them or seeing them. [Delhi 2016C]

Answer/Explanation

Answer:
Explaination: Tiger census is carried out by counting the pug marks or faecal pellets.


66. Define natality.

Answer/Explanation

Answer:
Explaination: Natality is defined as the number of births that are added to the initial density in a population during a given period of time.


67. Define mortality.

Answer/Explanation

Answer:
Explaination: Mortality refers to the number of deaths in the population during a given period.


68. What does nature’s carrying capacity for a species indicate? [Foreign 2016]

Answer/Explanation

Answer:
Explaination: It refers to the maximum number of individuals of a population that the given environment can sustain with its resources.


69. Name two organisms (one plant and one animal) which breed only once in their lifetime.

Answer/Explanation

Answer:
Explaination: Bamboo; Pacific Salmon Fish.


70. Why have life history variations evolved?

Answer/Explanation

Answer:
Explaination: Life history variations have evolved in organisms to maximise their reproductive fitness or Darwinian fitness in their natural habitats.


71. Mention any two reasons why plants depend on other organisms for their survival, even though they make their own organic food.

Answer/Explanation

Answer:
Explaination:
(i) Plants depend on animals (mainly insects) for pollination.
(ii) They also depend on animals for dispersal of seeds and/or fruits.
(iii) They depend on the soil microbes, which can carry out decomposition of organic matter and return the inorganic nutrients to the soil for absorption by plants. (any two)


72. Why are cattle and goats not browsing the Calotropis growing in the fields? [Foreign 2011]

Answer/Explanation

Answer:
Explaination: Calotropis plants produce highly toxic cardiac glycosides; hence, the cattle avoid browsing them.


73. Write one common feature among predation, parasitism and commensalism.

Answer/Explanation

Answer:
Explaination: In all these, the interacting species live closely together and one of the species is benefitted.


74. What term is given to the predators of plants.

Answer/Explanation

Answer:
Explaination: Herbivores.


75. What type of interaction is shown by a sparrow eating the seeds?

Answer/Explanation

Answer:
Explaination: Predation.


76. An exotic variety of prickly pear introduced into Australia turned out to be invasive. How was it brought under control? [Delhi 2013C]

Answer/Explanation

Answer:
Explaination: By introducing a cactus-feeding moth.


77. Why are predators ‘prudent’ in nature? [HOTS]

Answer/Explanation

Answer:
Explaination: Predators are prudent in nature because if a predator is too efficient and over-exploits its prey, then the prey might become extinct and following it, the predator will also become extinct.


78. Why do predators avoid eating monarch butterfly? How does the butterfly develop this protective feature? [Foreign 2010]

Answer/Explanation

Answer:
Explaination:
– The monarch butterfly is highly distasteful to the predators.
– It is due to a chemical present in its body; the butterfly acquires this chemical during its caterpillar stage, by feeding on a poisonous weed.


79. Write what the phytophagous insects feed on. [Delhi 2012]

Answer/Explanation

Answer:
Explaination: Phytophagous insects feed on the sap and other parts of the plants.


80. Why is the problem of predation in plants more severe than that in animals? [HOTS]

Answer/Explanation

Answer:
Explaination: Problem of predation is severe for plants because they cannot move away from their predators.


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